Resistive random access memory and method for manufacturing the same

ABSTRACT

A resistive random access memory including, an insulating layer, a hard mask layer, a bottom electrode, a memory cell and a top electrode is provided. The insulating layer is disposed on the bottom electrode. The insulating layer has a contact hole having a first width. The hard mask layer has an opening. A portion of the memory cell is exposed from the opening and has a second width smaller than the first width. The top electrode is disposed on the insulating layer and is coupled with the memory cell.

This application is a divisional application of co-pending U.S.application Ser. No. 11/898,529, filed Sep. 13, 2007.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates in general to a resistive random access memory andmethod for manufacturing the same, and more particularly to a resistiverandom access memory and a method for manufacturing the same capable ofreducing the width of the memory cell without a mask and increasingresistance.

2. Description of the Related Art

Along with the advance in semi-conductor technology, electronic elementsare kept being miniaturized, such that electronic products possess moreand more functions when the size remains unchanged or become evensmaller. As there are more and more information to be processed, thedemand for the memory having larger capacity but smaller size is everincreasing.

Currently, the read-write memory stores data by means of a transistorstructure assisted by a memory cell. However, the technology formanufacturing such memory has come to a bottleneck in terms ofscalability. Therefore, more advanced memory structures, such as phasechange random access memory (PCRAM), magnetic random access memory(MRAM), and resistive random access memory (RRAM), are presented. TheRRAM, having the advantages of fast read-write speed, non-destructiveaccess, tolerance against extreme temperatures and compatibility withcurrent manufacturing process of complementary metal oxide semiconductor(CMOS), is a new memory technology with great potential to replace thecurrent storage media.

Currently, RRAM still has much to improve in mass production, needs totackle with the problems of leakage current and high power consumption,and still has to overcome many other problems before commercialapplication matures.

SUMMARY OF THE INVENTION

The invention is directed to a resistive random access memory and amethod for manufacturing the same. The memory cell manufacturedaccording to the manufacturing method of the invention without using themask manufacturing process can break the limit of the lithographytechnology, hence increasing resistance and reducing power consumption.

According to a first aspect of the present invention, a resistive randomaccess memory including an insulating layer of a bottom electrode, ahard mask layer, a memory cell and a top electrode is provided. Thebottom electrode is disposed on the substrate. The insulating layer isdisposed on the bottom electrode. The insulating layer has a contacthole having a first width. The hard mask layer has an opening. A portionof the memory cell exposed from the opening has a second width smallerthan the first width. The top electrode is disposed on the insulatinglayer and is coupled with the memory cell.

According to a second aspect of the present invention, the manufacturingmethod of resistive random access memory includes the following steps.First, a bottom electrode is formed. Next, an insulating layer is formedon the bottom electrode, wherein the insulating layer has a contact holehaving a first width. Then, a spacer having a first opening is formed inthe contact hole, wherein the first opening has a second width smallerthan first width. Next, a memory cell having a second width is formed.Then, a top electrode coupled with the memory cell is formed.

The invention will become apparent from the following detaileddescription of the preferred but non-limiting embodiments. The followingdescription is made with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1G are schemes showing the manufacturing process of a resistiverandom access memory according to a first embodiment of the invention;

FIG. 2 is a flowchart of the manufacturing process of a resistive randomaccess memory according to the first embodiment of the invention;

FIGS. 3A-3H are schemes showing the manufacturing process of a resistiverandom access memory according to a second embodiment of the invention;

FIG. 3I is a plan view of the semiproduct of resistive random accessmemory of FIG. 3G.

FIG. 4 is a flowchart of the manufacturing process of a resistive randomaccess memory according to the second embodiment of the invention;

FIG. 5 is a scheme of another resistive random access memory accordingto a second embodiment of the invention;

FIGS. 6A-6E are schemes showing the manufacturing process of a resistiverandom access memory according to a third embodiment of the invention;

FIG. 6F is a plan view of the semiproduct of resistive random accessmemory of FIG. 6D.

FIG. 7 is a flowchart of the manufacturing process of a resistive randomaccess memory according to a third embodiment of the invention; and

FIG. 8 is a scheme of another resistive random access memory accordingto a third embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION First Embodiment

Referring to FIGS. 1A-1G, schemes showing the manufacturing process of aresistive random access memory according to a first embodiment of theinvention are shown. Also referring to FIG. 2, a flowchart of themanufacturing process of a resistive random access memory according tothe first embodiment of the invention is shown. Referring to FIG. 1A,first, the manufacturing process begins at step 201, a bottom electrode110 is formed on a substrate 100, wherein the substrate 100 is a siliconwafer for example, and the bottom electrode 110 is made ofaluminum-copper alloy or tungsten. Next, the manufacturing processproceeds to step 202, a nitride layer 120 is formed on the bottomelectrode 110, wherein the nitride layer 120 is exemplified by siliconnitride in the present embodiment of the invention. Then, themanufacturing process proceeds to step 203, an insulating layer 130 isformed on the nitride layer 120. In the present step, silicon oxide ortetraethoxysilan (TEOS) is deposited via plasma enhanced chemical vapordeposition (PECVD), or silicon oxide is deposited according to lowpressure chemical vapor deposition (LPCVD). Preferably, after theinsulating layer 130 is deposited, the insulating layer 130 isplanarized according to chemical mechanical polishing (CMP) method.

Referring to FIG. 1B, as indicated in step 204, the insulating layer 130is etched as an insulating layer 130 a to form a contact hole 132 havinga width W1. The present step can use a mask manufacturing processassisted by reactive ion etching (RIE) method to form the contact hole132. The nitride layer 120 is used as an etching stopper layer herein,and is also an excellent anti-oxidation barrier material used in thefollowing process.

Referring to FIG. 1C, as indicated in step 205. First, the spacermaterial layer (not illustrated) is deposited, wherein the spacermaterial layer is made of silicon oxide. In the present step, the spacermaterial layer is formed by way of thermal evaporation, e-beamevaporation, or molecular beam epitaxy (MBE) system. Next, the spacer isetched to form a spacer 140 in contact hole 132, wherein the spacer 140has an opening 142 on the bottom. The spacer material layer can beetched via RIE method. The opening 142 has a width W3 smaller than thewidth W1 of the contact hole 132, wherein the width W3 is approximatelyequal to 100 nm. The width W2 of the spacer 140 ranges between 60-100nm, and is substantially equal to the deposited thickness of the spacermaterial layer. The etching step is achieved by way of reactive ionetching (RIE) method assisted by F-based chemistries such as CF₄, C₄F₈,CHF₃ and CH₃F.

Referring to FIG. 1D, as indicated in step 206, the nitride layer 120exposed from the opening 142 is etched to form a nitride layer 120 ahaving an opening 122. Likewise, the opening 120 a substantially has awidth W3.

Referring to FIG. 1E, as indicated in step 207, the spacer 140 isremoved so that the infilling material is able to enter into the contacthole 132.

Referring to FIG. 1F, as indicated in step 208, the bottom electrode 110is oxidized as a bottom electrode 110 a so as to form the memory cell112. As the nitride layer 120 a is a hard mask layer and can be used asan excellent anti-oxidation barrier, such that the memory cell 112formed by way of oxidation is positioned within the part exposed by theopening 122 and has a width W3, and the unexposed part of bottomelectrode 110 is protected from oxidizing. In the present step, thetemperature is controlled to be between 200° C.-300° C. by a furnace orrapid thermal processing (RTP) system, and the pressure is controlled tobe within the range of several mtorr to 1 atm for minutes or hours undera mixed gas environment of oxygen and nitrogen.

Or, the surface of the bottom electrode 110 is oxidized by plasma undera mixed gas environment of pure oxygen (O₂), oxygen and argon mixture(O₂/Ar), or argon, oxygen and nitrogen mixture (Ar/O₂/N₂), the pressureis controlled to be within the range of 1 mtorr to 100 mtorrs, and thetemperature is controlled to be between the room temperature and 300° C.

Referring to FIG. 1G, as indicated in step 209, a top electrode 150coupled with the memory cell 112 is formed, and a resistive randomaccess memory 10 is completed. The resistive random access memory 10comprises the substrate 100, the bottom electrode 110 a, the nitridelayer 120 a, the insulating layer 130 a, the memory cell 112 and the topelectrode 150. The bottom electrode 110 a is disposed on the substrate100, the nitride layer 120 a is disposed between the bottom electrode110 a and the insulating layer 130 a.The memory cell 112 exposed fromthe opening 122 has a width W3 smaller than the width W1, and ispositioned inside the bottom electrode 110 a.The insulating layer 130 ais disposed on the nitride layer 120 a and has the contact hole 132having the width W1. The top electrode 150 is disposed on the insulatinglayer 130 a and is coupled with the memory cell 112.

The top electrode 150 and the bottom electrode 110 a can only be coupledthrough the memory cell 112, such that the memory cell 112 manufacturedaccording to the manufacturing method of the present embodiment of theinvention reduces the area of the memory cell 112 without using anadditional mask, but increases the resistance between the top electrode150 and the bottom electrode 110 a.Therefore, less current is generatedunder the same operating voltage, not only reducing the overall powerconsumption but also reducing the damage incurring to the memory cell,hence increasing the reliability of overall device. Furthermore, thethreshold voltage required for changing the bit state of the memory cell112 can be reduced to be around 3.4V, further increasing theavailability of the resistive memory.

Second Embodiment

Referring to FIGS. 3A-3H, schemes showing the manufacturing process of aresistive random access memory according to a second embodiment of theinvention are shown. Also referring to FIG. 4, a flowchart of themanufacturing process of the resistive random access memory according toa second embodiment of the invention is shown. The steps and elementcharacteristics of the present embodiment of the invention common tothat of the first embodiment are not repeated here. Referring to FIG.3A, the manufacturing process begins at step 401, first, a bottomelectrode 310 is formed on the substrate 300. Next, the manufacturingprocess proceeds to step 402, an insulating layer 320 is formed on thebottom electrode 310.

Referring to FIG. 3B, as indicated in step 403, the insulating layer 320is etched as an insulating layer 320 a so as to form a contact hole 322having a width W4.

Referring to FIG. 3C, as indicated in step 404, a conductive layer 330is formed in the contact hole 322. In the present embodiment of theinvention, the conductive layer 330 is made of tungsten.

Referring to FIG. 3D, as indicated in step 405, the conductive layer 330is planarized as a conductive layer 330 a.The present step is achievedby way of CMP.

Referring to FIG. 3E, as indicated in step 406, the conductive layer 330a is etched for creating a distance between the surface of theconductive layer 330 b and the surface of the insulating layer 320 a.

Referring to FIG. 3F, as indicated in step 407, a spacer 340 is formedin the contact hole 322, wherein the spacer 340 has an opening 342having a width W6 smaller than the width W4. The width W5 is distantfrom the inner edge of bottom of the spacer 340 to the insulating layer320 a.The width ranges between 60-100 nm and is substantially equal tothe deposited thickness of the spacer material layer. In the presentembodiment, the material of the spacer 340 is silicon oxide.

Referring to FIG. 3G, as indicated in step 408, the conductive layer 330b is oxidized as a conductive layer 330 c so as to form the memory cell332. Referring to FIG. 3I, a plan view of the semiproduct of resistiverandom access memory of FIG. 3G is shown. As shown in FIG. 3I, thespacer 340 positioned inside the contact hole 322 has an opening 342 forexposing the memory cell 332.

Referring to FIG. 3H, as indicated in step 409, the top electrode 350coupled with the memory cell 332 is formed. Up to now, the resistiverandom access memory 20 is completed. The resistive random access memory20 includes the substrate 300, the bottom electrode 310, the insulatinglayer 320 a, the conductive layer 330 c, the memory cell 332, the spacer340 and the top electrode 350. The bottom electrode 310 is disposed onthe substrate 300. The insulating layer 320 a is disposed on the bottomelectrode 310. The insulating layer 320 a has a contact hole 322 havinga width W4. The conductive layer 330 c is disposed in the contact hole322. A hard mask layer exemplified by spacer 340 is disposed above thebottom electrode 310, that is, on the conductive layer 330 c.The memorycell 332 positioned on the conductive layer 330 c is exposed from thecontact hole 322. The spacer 340 is disposed in the contact hole 322 andhas an opening 342 having a width W6 smaller than width W4. A portion ofthe memory cell 332 exposed from the opening 342 has a width W6. Thewidth of the opening 342 is substantially equal to the width of thememory cell 332. The top electrode 350 is disposed on the insulatinglayer 320 a and is coupled with the memory cell 332.

Referring to FIG. 5, a scheme of another resistive random access memoryaccording to the second embodiment of the invention is shown. Theresistive random access memory 30 differs with the resistive randomaccess memory 20 in that the resistive random access memory 30 has anoxide layer 334 disposed on the conductive layer 330 d and the memorycell 332 is a portion of the oxide layer 334. The manufacturing processof the resistive random access memory 30 differs with that of resistiverandom. access memory 20 in that after the step 406 is performed, thestep 408 is performed before the step 407. That is, the conductive layer330 b is oxidized as a conductive layer 330 d to form the oxide layer334 first, and the spacer 340 is formed in the contact hole 322afterwards. Thus, the top. electrode 350 and the bottom electrode 310can only be coupled through the memory cell 332 having width W6, suchthat the resistance is increased.

Third Embodiment

Referring to FIGS. 6A-6E, schemes showing the manufacturing process of aresistive random access memory according to a third embodiment of theinvention are shown. Also referring to FIG. 7, a flowchart of themanufacturing process of a resistive random access memory according tothe third embodiment of the invention is shown. The steps and elementcharacteristics of the present embodiment of the invention common tothat of the first embodiment or the second embodiment are not repeatedhere.

Referring to FIG. 6A, the manufacturing process begins at step 701,first, a bottom electrode 610 is formed on the substrate 600, and thisbottom electrode 610 is made of tungsten. Next, the manufacturingprocess proceeds to step 702, an insulating layer 620 is formed on thebottom electrode 610.

Referring to FIG. 6B, as indicated in step 703, the insulating layer 620is etched as an insulating layer 620 a so as to form a contact hole 622having a width W7.

Referring to FIG. 6C, as indicated in step 704, a spacer 630 having anopening 632 is formed, wherein the opening has a width W9 smaller thanthe width W7. Likewise, the width W8 is distant from the inner edge ofthe spacer 630 to the insulating layer 620 a.The width W8 ranges between60-100 nm and is substantially equal to the deposited thickness of thespacer material layer. In the present embodiment, the material of thespacer is silicon oxide.

Referring to FIG. 6D, as indicated in step 705, the bottom electrode 610is oxidized as a bottom electrode 610 a so as to form the memory cell612. Referring to FIG. 6F, a plan view of the semiproduct of resistiverandom access memory of FIG. 6D is shown. As shown in FIG. 6F, thespacer 630 positioned inside the contact hole 622 has an opening 632 forexposing the memory cell 612.

Referring to FIG. 6E, as indicated in step 706, the top electrode 640coupled with the memory cell 612 is formed to complete the resistiverandom access memory 40. The resistive random access memory 40 includesa substrate 600, a bottom electrode 610 a, an insulating layer 620 a, aspacer 630, a memory cell 612 and a top electrode 640. The bottomelectrode 610 a is disposed on the substrate 600. The insulating layer620 a is disposed on the bottom electrode 610 a.The insulating layer 620a has a contact hole 622 having a width W9. The memory cell 612 isexposed from the contact hole 622. A hard mask layer exemplified by thespacer 630 is disposed on the bottom electrode 610 a.The spacer 630 isdisposed in the contact hole 622 and has an opening 632 having a widthW9. The width of the opening 632 and the width of the exposed portion ofthe memory cell 612 are substantially the same, and the width W9 issmaller than the width W7. The top electrode 640 is disposed on theinsulating layer 620 a and is coupled with the memory cell 612. In thepresent embodiment of the invention, the memory cell 612 is positionedon the bottom electrode 610 a preferably made of tungsten.

Referring to FIG. 8, a scheme of another resistive random access memoryaccording to the third embodiment of the invention is shown. Theresistive random access memory 50 differs with the resistive randomaccess memory 40 in that the resistive random access memory 50 furtherincludes an oxide layer 614 disposed on the bottom electrode 610 b, andthe memory cell 612 is a portion of the oxide layer 614. Themanufacturing process of the resistive random access memory 50 differswith that of the resistive random access memory 40 in that after thestep 703 is performed, the step 705 is performed before the step 704.That is, after the contact hole 622 is formed first, the bottomelectrode 610 is oxidized as a bottom electrode 610 b so as to form theoxide layer 614 afterwards. Then, a spacer 630 is formed in the contacthole 622. Thus, the top electrode 640 and the bottom electrode 610 b canonly be coupled through the memory cell 612 having width W9, such thatthe resistance is increased.

According to the resistive random access memory and method formanufacturing the same disclosed in the above embodiments of theinvention, forming the hard mask together with dry ehcting replaces themask process, hence breaking through the resolution restriction of theexposing machine to form a small-sized memory cell. The resistive randomaccess memory manufactured via the method of the invention increasesresistance and possesses the characteristics of low power consumptionand low threshold voltage, hence increasing the practicality andapplication of the resistive random access memory.

While the invention has been described by way of example and in terms ofpreferred embodiments, it is to be understood that the invention is notlimited thereto. On the contrary, it is intended to cover variousmodifications and similar arrangements and procedures, and the scope ofthe appended claims therefore should be accorded the broadestinterpretation so as to encompass all such modifications and similararrangements and procedures.

What is claimed is:
 1. A manufacturing method of resistive random accessmemory, comprising: (a) forming an insulating layer, wherein theinsulating layer has a contact hole having a first width; (b) forming aspacer in the contact hole, wherein the spacer has a first openinghaving a second width smaller than the first width; (c) forming a memorycell having the second width positioned beneath the spacer; and (d)forming a top electrode coupled with the memory cell.
 2. Themanufacturing method according to claim 1, further comprising forming ananti-oxidation barrier material, wherein the insulating layer is formedon the anti-oxidation barrier material.
 3. The manufacturing methodaccording to claim 2, further comprising etching the anti-oxidationbarrier material so as to form an anti-oxidation barrier having a secondopening, wherein the second opening has the second width.
 4. Themanufacturing method according to claim 1, wherein between step (a) andstep (b), the method further comprises forming a conductive layer in thecontact hole; planarizing the conductive layer to expose the insulatinglayer; and etching the conductive layer for creating a distance betweenthe surface of the conductive layer and the surface of the insulatinglayer.
 5. The manufacturing method according to claim 4 furthercomprising oxidizing the conductive layer prior to step (b).
 6. Themanufacturing method according to claim 4, wherein the step (d) furthercomprises oxidizing the conductive layer.
 7. The manufacturing methodaccording to claim 1, further comprising forming a bottom electrode,wherein the insulating layer is formed on.
 8. The manufacturing methodaccording to claim 7, further comprising oxidizing the bottom electrodeprior to the step (b).
 9. The manufacturing method according to claim 7,wherein the step (c) further comprises oxidizing the bottom electrode soas to form an oxide layer having the memory cell positioned therein. 10.A manufacturing method of resistive random access memory, comprising:(a) forming an insulating layer, wherein the insulating layer has acontact hole having a first width; (b) forming a spacer in the contacthole, wherein the spacer has a first opening having a second widthsmaller than the first width; (c) forming a memory cell having thesecond width; and (d) forming a top electrode coupled with the memorycell; wherein the method further comprising: forming an anti-oxidationbarrier material, wherein the insulating layer is formed on theanti-oxidation barrier material; etching the anti-oxidation barriermaterial so as to form an anti-oxidation barrier having a secondopening, wherein the second opening has the second width; and removingthe spacer.
 11. The manufacturing method according to claim 10, furthercomprising forming a bottom electrode, wherein the insulating layer isformed on.
 12. The manufacturing method according to claim 11, furthercomprising oxidizing the bottom electrode prior to the step (b).
 13. Themanufacturing method according to claim 11, wherein the step (c) furthercomprises oxidizing the bottom electrode so as to form an oxide layerhaving the memory cell positioned therein.